This invention relates to dishwashers and in particular but not solely to a dishwasher of the type disclosed in the applicant""s international patent specification WO 93/12706.
The dishwasher of WO 93/12706 has a form generally indicated in FIGS. 1 and 2 and installation options as shown in FIGS. 4 to 6. The dishwasher disclosed in WO 93/12706 differs from conventional dishwashers in that a wash chamber and associated wash system is slidably mounted in the form of a drawer within a cabinet and the chamber is withdrawn horizontally to allow leading through the open top of the chamber. When the chamber is retracted an associated lid sealably closes off the top of the chamber to contain wash liquid in operation. In WO 93/12706 the wash chamber lid is of unitary construction movably retained in the top of the cabinet and engaged by the wash chamber on retraction to move down onto the top of the wash chamber using a parallelogram linkage and cam mechanisn. In practice it has been found that other types of wash chamber covers may be satisfactory and may have better production economics.
Detergent dispensers are a necessary component of all dishwashers. Conventional dispensers retain a charge of detergent until an appropriate point in the wash cycle, at which time a detergent receptacle opens to release detergent into the wash chamber. Conventional dispensers have the disadvantage that considerable quantities of high pressure liquid need to enter the detergent receptacle to sure it is properly flushed and where the receptacle uses a moving door to release the detergent the opening of the door can be obstructed by the wash load.
In the previously mentioned WO 93/12706 a dishwasher drain pump was disclosed. While the drain pump there described operated satisfactorily, particles in the soiled wash water could be deposited in the gap between the motor rotor and well 106.
In WO 93/12706 a dishwasher was disclosed having a cabinet containing single wash chamber and associated wash system. Because a sliding drawer type configuration exerts more forces on the cabinet than front loading machines portal frame members were proposed to increase the racking resistance of the cabinet. In WO 93/12706 it was envisaged that increased dishwashing capacity could be achieved by simply increasing the number of discrete dishwasher modules, Particular reference was made to mounting two modules under a kitchen bench one above the other. The height of each module was chosen to ensure that when two modules were mounted in the kitchen joinery one above they other they would fit within the bench height of typical household kitchens. In some circumstances an integral two wash tub dishwasher may be preferredxe2x80x94that is, a cabinet having two drawers instead of one. This however increases the problem of providing adequate resistance to racking forces exerted by the wash tabs since the xe2x80x98openxe2x80x99 fronted cabinet is then required to be approximately twice the height of a single drawer cabinet.
It is an object of the present invention to provide a dishwasher of the type described having an effective wash chamber closure sealing system.
It is a further object of the present invention to provide a dishwasher detergent dispenser which at least goes some way towards overcoming the above-mentioned disadvantages.
Further objects of the invention are to provide:
a dishwasher with an improved drain pump,
a dishwasher cabinet for housing two wash chambers,
a dishwasher water management system, and
a heating element fault protection circuit
In one aspect the present invention consists in a washing appliance comprising:
(a) a cabinet,
(b) a wash system slidably mounted within said cabinet in such a manner that it may be withdrawn horizontally out of said cabinet for access thereto, said wash system including:
(i) an open top wash chamber adapted to accommodate dishes within which wash liquid is circulated, said wash chamber having a top peripheral rim,
(ii) means for introducing and circulating wash liquid within said chamber,
(iii) means for evacuating wash liquid from said chamber,
(c) a wash chamber closure mounted in the top of said cabinet, which closure covers the open top of said wash chamber on retraction of the wash chamber into said cabinet,
(d) said closure having peripheral means which cooperate with said rim to prevent egress of wash liquid from the wash chamber when it is retracted into said cabinet, and said closure being retained in a substantially fixed vertical position in the top of said cabinet.
In a further aspect the invention consists in a washing appliance comprising:
(a) a cabinet
(b) a wash system slidably mounted within said cabinet in such a manner that it may be withdrawn horizontally out of said cabinet for access thereto, said wash system including:
(i) an open top wash chamber adapted to accommodate items to be washed and within which wash liquid is circulated, said wash chamber having a top peripheral rim,
(ii) means for introducing and circulating wash liquid within said chamber,
(iii) means for evacuating wash liquid from said chamber,
(c) a wash chamber closure mounted in the top of said cabinet, which closure covers the open top of said wash chamber on retraction of the wash chamber into said cabinet,
(d) said closure being mounted in the top of said cabinet by mechanical means which permit it to move in a vertical direction only and said closure having peripheral means which cooperate with said rim to prevent egress of wash liquid from the wash chamber when it is lowered from a raised position; and
(e) means for raising said closure prior to withdrawal of the wash system from the cabinet and lowering said closure on retraction of said wash system into said cabinet.
In yet a further aspect the present invention consists in a washing appliance as defined above wherein said lid is mounted in the top of said cabinet so as to lower when the wash chamber is retracted and raise when the wash chamber is withdrawn, the edge of said lid is provided with downward facing flanges and the rim of said wash chamber is provided with complementary upward facing flanges, the lid and rim flanges loosely inter-engaging when the lid is lowered to form a labyrinthic seal there between.
In a further aspect the invention consists in a dishwasher, including a detergent dispenser mounted in one interior wall thereof and a controller which controls the sequence of operations executed by said dishwasher,
said detergent dispenser comprising:
a receptacle located behind said wall and communicating with the dishwasher interior through a vent in said wall,
an open top container for holding a charge of detergent mounted within said chamber,
a water outlet nozzle positioned above the open top of said container, and a supply valve which supplies water to said nozzle,
said controller causing said valve to open at a predetermined time in said cycle to cause water to be discharged from said nozzle into said container to mix with and flush said detergent charge through said vent into the interior of said dishwasher.
In yet a further aspect the present invention consists in a cabinet for a dishwasher having a box configuration with one open side and including a recessed kick plate along the bottom of the open side which cabinet provides resistance to racking forces applied parallel to the open side comprising:
a top, bottom, two side walls and a back wall of thin sheet material joined along their edges to leave a substantially rectangular front opening defined by the front edges of the top, bottom and two side walls,
the front edge of the bottom wall and the lowermost portions of the side walls being co-planar and recessed back from the front edges of the top wall and the upper portions of the side walls which lie in a second plane,
internally directed flanges on said front edges,
said flanges on the bottom and bottom side contiguous edges being rigidly joined at the two bottom corners and thereby configured as an inverted tapered beam portal frame with said two corners forming moment resisting joints,
rigid link members coupling the flanges on the lower recessed portions of the side walls to said flanges on the upper portions of the side walls and the flange on the top edge forming a beam linking the tops of the flanges on the upper portions of the side walls, the two joints defined by the intersections of the beam with the portal fame having no substantial resistance to bending moments.
In yet a further aspect the present invention consists in a dishwasher having a wash programme consisting of pre-rinse, wash, first post rinse and second post rinse cycles comprising:
first and second wash-chambers,
means for transferring wash liquid from the first wash chamber to the second wash chamber, and
a controller which implements said wash programme and which controls the operation of said transference means,
said controller:
(a) delaying the commencement of the wash programme for said second wash chamber until after the end of the first post rinse cycle in the wash programme for the first wash chamber,
(b) causing said transference means to transfer the rinse water from the first post rinse cycle of the first wash chamber from the first wash chambers to the second wash chamber,
(c) initiating the pre-rinse cycle for the second wash chamber using the first post rinse water from the first wash chamber,
(d) causing said transference means to transfer the rinse water from the second post rinse cycle of the first wash chamber from the first wash chamber to the second wash chamber, and
(e) initiating the wash cycle for the second wash chamber using the second post rinse water from the first wash chamber.
In yet a further aspect the present invention consists in a dishwasher comprising:
(a) a wash chamber adapted to accommodate dishes within which wash liquid is circulated,
(b) a cylindrical well provided in the floor of said chamber,
(c) an electric motor including:
(i) a rotor mounted within said well and
(ii) a co-acting stator mounted outside said wash chamber about the exterior surface of said well such that the cylindrical sides of said well lie in the rotor-stator air gap,
(d) a drain pump impeller mounted on the rotor drive shaft:in the well below the rotor,
(e) a sump formed in the floor of said wash chamber which is connected to the lower side wall of said well which houses said impeller by a conduit,
(f) a discharge tube connected to a different point about these surface of the lower side wall of said well which houses said impeller,
(g) said drain pump impeller comprising a disc, the periphery of which is closely adjacent to the side wall of said well to form a seal against fluid flow up the side of said well, said disc having a hub portion and blades formed on the lower surface thereof with the root of each blade radially spaced from the periphery of the hub portion to form an unimpeded annular fluid passage between the hub portion and the blades.
In yet a further aspect the present invention consists in a protection circuit for a resistive heating element powered from an alternating current supply comprising:
a current transformer the primary circuit of which comprises both the phase and neutral supply conductors connected across said heating element,
a secondary transformer winding across which a voltage its developed which is proportional to any out of balance current between the phase and neutral conductors respectively,
a third conductor forming a tertiary transformer circuit which is arranged to carry a very low bias current derived from said alternating current supply and to continuously develop a small predetermined voltage in the transformer secondary winding,
a direct current supply derived from said alternating current supply,
a relay coil and a transistor series connected across said direct current supply, the relay switch being connected in series with one of the alternating current supply conductors to the heating element,
a voltage sensing means connected to said secondary winding which provided said predetermined voltage is present across the secondary winding supplies enough current to said transistor to cause it to conduct sufficiently to allots a current to flow through said relay coil from said direct current supply which is sufficient to hold the relay switch on and to present an alternating voltage across said heating element, but in the event of failure to detect said predetermined voltage said voltage sensing means supplies insufficient current to said transistor to allow it to conduct enough current through the relay coil to retain the relay latched on.